Ethylene tetramerization with a highly active and long-lifetime trinuclear diphenylphosphinoamine/Cr(III)/MAO catalyst

The synthesis and characterization of a novel trinuclear diphosphinoamine ligand 2 are reported. The ligand combined with Cr(III), activated with methylaluminoxane, lead to highly active and long-lifetime catalytic systems for the tetramerization of ethylene to form 1-octene. The effects of reaction temperature, reaction pressure, molar ratio of Al/Cr and bis(diphenylphosphino)amine/Cr on the catalytic activity and product selectivity were studied. Compared with its mononuclear analogue 1, ligand 2 showed a higher catalytic activity and longer lifetime for ethylene tetramerization in the presence of methylaluminoxane as cocatalyst. High molecular weight polyethylene was generated as a by-product with extremely broad molecular weight distributions.

PREPARATIOPREPARATION OF 1-OCTENE BY ETHYLENE TETRAMERIZATION WITH HIGH SELECTIVITY

Two novel PNP ligands have been synthesized and characterized by 1H-NMR, elemen- tal analysis, and mass spectra. In combination with Cr(Ⅲ ) and cocatalyst MAO, they generate active catalytic systems that tetramerize ethylene with both high catalytic activity and high selectivity to produce 1-octene. The results show that these catalyst sys- tems are able to catalyze ethylene tetramerization, with high catalytic activity up to 0.89×106 g/mol Cr.h, and the selectivity of C8 in products is 72.52%, and the percentage of 1-olefins in the C8 cut is 97.87%.

A series of novel bisphosphinoamine ligands:Synthesis,characterization and application in ethylene tetramerization

A series of novel N-halogen-substituted-aryl bisphosphinoamine ligands were synthesized and characterized by elemental analysis,1H NMR and mass spectrometry.The combination of these ligands with Cr(Ⅲ) and activation by methylaluminoxane leads to highly active catalytic systems for the tetramerization of ethylene to form 1-octene.The catalytic activities and product selectivi-ties depend on the aryl ring substituents and the reaction conditions.We found that the location and size of the substituents are important in determining the catalytic activity and selectivity toward 1-octene.This trend is similar to that observed for their alkyl-substituted analogues.

Recent progress in immobilization of late-transition-metal complexes with diimine ligands for olefin polymerization

Late-transition-metal(LTM) catalysts are a family of very flexible ethylene polymerization catalysts because their catalytic performance can be easily adjusted by modifying the ligand structure.Their less oxyphilicity character,which may promote the production of copolymers from ethylene and polar comonomers,is another aspect that attracts much attention in both academic and industrial fields.The immobilization of LTM catalysts on spherical supports is a crucial step prior to their use in the industrial processes of gas-phase or slurry polymerizations.This paper reviews recent developments in supported LTM catalysts for olefin polymerization,and summarizes loading methods and mechanisms of the immobilization of LTM catalysts on inorganic,organic,and inorganic-organic materials,and the effects of immobilization on catalytic activity,polymerization mechanism,and polymer morphology.